Roof structures for frame houses, particularly roofs which have a wooden roofing surface are covered, usually, with a plurality of layers. The outer layers are formed by roofing shingles which are somewhat flexible and are formed with projecting separated flaps, overlying, horizontally staggered, a lower course of shingles. Each portion of the roofing surface, typically of wood or a wood product, thus is covered by a plurality of layers, formed, initially, by roofing felt or roofing paper, and then by a first layer of shingles. If the roof was re-shingled, a second layer of shingles is placed over the solid portion of the first shingles and over their flaps. The very first or edge course of the shingles usually has another starting strip therebeneath so that the gaps between the flaps of the first course are also covered.
When the shingles deteriorate, that is, when the surface granulation thereof has worn off, or if the roof becomes damaged due to storms, or for other causes, it is customary to reroof the house by placing another or second layer of shingles, over the old shingles. When that, second roofing layer becomes worn or damaged, it is usually not possible to add a third layer thereover, since the strength of the roofing structure may not be able to support the weight of yet another layer of roofing shingles. Thus, it is necessary to remove the shingles which are already on the roof, that is, usually two layers of shingles.
The shingles are nailed on the roof, usually with roofing nails which have wide flat heads, so that they can securely hold the soft shingle material. The nails are not visible, nor are they exposed to weather. The nails are placed along the upper edge portion of the shingles of any one course, so that, when the next course of shingles is laid thereover, they will be hidden under the flaps of the succeeding shingles. Since these shingles, again, are nailed and held down in the same manner, it is not possible to merely raise any one flap of a shingle in order to obtain access to the nails. The flaps frequently hide them and the succeeding layer of flaps--in an upward direction--tend to hold down the preceding ones. This hold-down effect is a substantial safety feature maintaining the integrity of the roof under stormy conditions. To remove the shingles, problems arise in obtaining access to the nails. One can work, of course, from the top down, that is, in reverse order from shingling the roof. Yet, to obtain access to the nails, and to pry them up on a nail-by-nail basis if two layers of shingles are on the roof is extremely time consuming and not customary in the field. Pry bars with extending blades have been proposed, arranged to fit beneath layers of shingles, or between the roof and the layer of shingles so that hopefully, a group of nails could be pried up from the roof boards at one time. The pry bars, however, have a limited life and tend to deform or break.